Electron discharge device filament structure



Aug. 12, 1969 Kwosm H M ET AL 3,461,337

ELECTRON DISCHARGE DEVICE FILAMENT STRUCTURE Filed Aug. 12, 1965INVENTORS 0s/// flaw/M400 BY 757500 75m 3 ATTORNEYS United States PatentUS. Cl. 313-278 6 Claims ABSTRACT OF THE DISCLOSURE A cage-like filamentsupport structure in which the filament wires are provided withintermediate supports connected to a movable support member, saidsupport member being freely slidable. on a centrally located fixedsupport in a direction generally parallel to said wires.

This invention relates to electron discharge device construction, andmore particularly to heating filaments for such devices.

It is an object of this invention to provide an improved type of supportfor electron discharge device filaments whereby long length filamentsare supported in a mor reliable and satisfactory manner.

Another object is to provide a filament support having a longer lifethan prior support arrangements.

All of the objects, features and advantages of this invention and themanner of attaining them will become more apparent and the inventionitself will be best understood by reference to the following descriptionof an embodiment of the invention taken in conjunction with theaccompanying drawing, in which:

FIG. 1 is a diagrammatic side view of a heating filament assembly foruse in an electron discharge device,

FIG. 2a is an enlarged vertical sectional view of an intermediatesupport and insulating structure for heating filaments according to oneembodiment of the invention,

FIG. 2b is a perspective view of the binding wire supporting portion ofsaid filaments,

FIGS. 3aand 3b are views similar to FIGS. 201 and 2b, but of theconventional intermediate support and insulating portion,

FIGS. 4 and 5 are views illustrating deformation of the binding wire andthe heating filament incorporated in a conventional assembly, and

FIGS. 6a and 6b, and 7a and 7b are views corresponding to FIGS. 2a and2b showing modifications of the latter embodiment of the invention.

In a cage-like assembly of heating filaments comprising a multiplicityof element wires 1 arranged as shown in FIG. 1, it has been necessary toprovide a plurality of supports at intermediate positions along thelength of the assembly, as well as a central pole, in order to preventdeformation, vibration, listing, and the like of the element wires,because of their length. With such an assembly of heating elements, theheating current usually flows along every other element wire arrangedparallel to one another, so that the directions of the currents inadjoining wires are opposite to one another, as indicated by the arrowsin FIG. 1. As a consequence, there is a drop of the heater voltage alongthe axial direction of the filaments. It has therefore been necessary tobind and support every other filament at the points of same potentialwith metallic wires or conductors 2, 2'. Thus, when two intermediatesupports which are to support the points "Ice of difierent potential areto be fitted to a common central pole 5, the intermediate supports andthe central pole 5 must be insulated from each other.

In a conventional structure as shown in FIGS. 3a and 3b, theintermediate supports comprise binding wires 2 of heat-resistant metalsuch as tungsten or molybdenum which directly support filaments 1, andbinding wire holders 3 also of heat-resistant metal. The holders 3 aresupported by heat-resistant insulators 4, of for example, talc,steatite, or alumina ceramic. These insulators 4 are fixed to a centralpole 5, in such a manner that the filament wires 1 and binding wires 2are slidable along the supporting points 7 upon thermal expansion onheating or contraction on cooling of the filaments. With such astructure however, if the filaments are heated to a high temperature,the binding wires 2 tend to become baked on the filaments 1, so thatslidable movement between these wires 2 and the filaments 1 at thesupporting points 7 cannot occur. Thus, whenever the filaments 1 areheated or cooled, the binding wires 2 are pulled up or down by thefilaments 1 as indicated by the dashed lines in FIG. 30, until the wires2 are ultimately broken. Another disadvantage is that, because thebinding wires 2 are not wound completely around the filaments,deformation of the filament wires due to inward deflection of thefilaments as indicated in FIG. 5 cannot be avoided.

The present invention eliminates all of the foregoing difl'iculties, andprovides a cage-like assembly of heating filaments protected againstdeformation, since intermediate supports which hold the heatingfilaments in place are made freely slidable upon the expansion andcontraction of the filaments in the longitudinal direction. In oneembodiment of the invention, illustrated in FIGS. 2a and 2b, eachbinding wire 2 is wound securely around a filament 1, and eachintermediate support comprising a binding wire 2 and a binding wireholder 3 is fixed to a heat-resistant insulator 4, which in turn is heldfor slidable movement on a central pole 5. Also provided are upper andlower limiters 6 each spaced from the insulator 4 a distance equivalentto or greater than the amount of expansion and contraction of thefilament 1. By such construction all the intermediate supports and theinsulators 4 of the assembly can slide upward or downward along thecentral pole, according to the expansion or contraction of the filaments1 on heating or cooling, as the case may be. It will thus be appreciatedthat'the binding wires 2 in such an assembly will not be bent upward ordownward, and any possibility of inward deformation of the filaments asshown in FIG. 5 is prevented. The intermediate supports may be fixed tothe insulators 4 by inserting the supports from the upper and lowerportions of the insulators 4 as shown in FIG. 2, or by laminating theinsulators and the intermediate supports alternately and fixing theuppermost layer with a retainer 8 as shown in FIG. 6a, or by any othersuitable method. What have thus far been described are merely preferredembodiments of the present invention, and it is of course to beunderstood that the invention is also applicable to an assembly whereinthe binding wires are fitted directly to the insulators in a suitablem-anner, as illustrated in FIGS. 7a and 7b. It will further beunderstood that various different arrangements may be provided wherebythe insulator 4 may moves relative to the pole 5 upon expansion andcontraction of the filament wires.

While the foregoing description sets forth the principles of theinvention in connection with specific apparatus, it is to be understoodthat the description is made only by way of example and not as alimitation of the scope of the invention as set forth in the objectsthereof and in the accompanying claims.

What is claimed is:

1. A heating filament support structure for an electron discharge devicecharacterized in that binding wires are provided which support theheating filaments and are fixed to a heat-resistant insulator throughthe medium of attachment of binding wire holders of heat-resistantmetal,

said heat-resistant insulator being supported on a central pole in agiven position thereon solely by reason of the attachment thereof tosaid filaments and unbiased in the longitudinal direction thereof, andsaid insulator also being freely slidable upward and downward on saidcentral pole in accordance with expansion and contraction of the heatingfilaments in the longitudinal direction.

2. In combination,

an array of heating filament strands which change in length upon heatingand cooling thereof,

a first support member positioned amidst said array,

a second member supported on said first member in a given positionthereon solely by reason of the connection of said first and secondmeans to said strands and unbiased in the longitudinal directionthereof,

first means connected to said strands intermediate the length thereoffor restraining lateral movement of said strands,

second means connecting said first means to said second member,

said second member being freely slidable in a first direction generallyparallel to said filament strands upon heating thereof, and said secondmember also being freely slidable in the direction opposite to saidfirst direction upon cooling of said filament strands.

3. The invention described in claim 2 wherein said first means compriseswires wound around said strands.

4. The invention described in claim 2 wherein said first membercomprises a cylindrical support positioned centrally in said array.

5. The invention described in claim 4 wherein said second membercomprises an insulator having a central aperture, said insulator beingslidably mounted on said cylindrical support with the latter passingthrough said aperture.

6. In an electron discharge device, the combination comprising aplurality of heating filament strands which change in length uponheating and cooling thereof, said filaments being positioned relative toone another to form a cage-like structure,

a fixed member disposed generally centrally within said structure andgenerally parallel to said strands,

a movable member having an aperture therein, said movable member beingmounted on said fixed member with said latter member passing throughsaid aperture to provide slidable movement of said movable memberrelative to said fixed member,

means connected to each of said filament strands intermediate the lengththereof and to said movable member for restraining lateral movement ofsaid strands.

said movable member being supported in a given position on said fixedmember solely by reason of the connection of said means between saidstrands and said movable member,

said movable member being unbiased in the longitudinal direction of itsmovement on said fixed member,

said second member being freely movable in a first direction generallyparallel to said filament strands upon heating thereof, and said secondmember being freely movable in the direction opposite to said firstdirection upon cooling of said filament strands.

References Cited UNITED STATES PATENTS 1,723,904 8/ 1929 White 313-2761,819,146 8/1931 Bol 313-273 X 1,927,084 9/ 1933 Depew 313-278 2,344,5523/1944 Knochel et a1. 313-278 2,385,435 9/1945 Werner et al 313-278 JOHNW. HUCKERT, Primary Examiner A. J. JAMES, Assistant Examiner US. Cl.X.R. 313-273, 276

